Drilling apparatus



SePt- 2, 1969 R. P. VINCENT ETAL 3,464,505

DRILLING APPARATUS 4 Sheets-Sheet 1 Filed NOV. l, 196'? LMI E RENIC P. VINCENT LAWRENCE B. WILDER INVENTORS.

ATTORNEY.

FIG-1A sept 2, 969 R. P. VINCENT ETAL 3,464,505

DRILLING APPARATUS RENIC i P VINCENT LAWRENCE B. WILDER INVENTORS.

AT TORNE Y.

SCP- 2 w69 R. P. vlNcENT ETAL 3,464,505

DRILLING APPARATUS 4 Sheets-Sheet 5 Filed Nov. 1, 1967 RENIC fp. VINCENT LAWRENCE B. WILDER INVENTORS;

ATTORNEY 4 Sheets-Sheet 4 INVENTORS ATTORNEY RENIC P. VINCENT LAWRENCE B. WILDER Sept. 2, 1969 R. P. VINCENT ETAL E DRILLING APPARATUS Filed Nov. l, 1967 United States Patent 3,464,505 DRILLING APPARATUS Renic Price Vincent and Lawrence B. Wilder, Tulsa,

Okla., assignors to Pan American Petroleum Corporation, Tulsa, Okla., a corporation of Delaware Continuation-impart of application Ser. No. 491,116, Sept. 29, 1965. This application Nov. 1, 1967, Ser. No. 691,082

Int. Cl. E21b 1/06 U.S. Cl. 173-80 23 Claims ABSTRACT F THE DISCLOSURE This invention relates to a liquid actuated percussion tool for applying repeated blows to a drill bit in the drilling of wells. The tool is connected to the lower end of the drill string just above the bit. The tool includes a hammer slideably tted within a housing, an axially hollow anvil fitted within the housing and below the lower end of the hammer. The hammer is actuated between an upward position away from and a lower position contacting the anvil by a valve action on a uid stream flowing in the axial hollow portion. The valve means includes an inner annular valve seat on the hammer which is positioned such that the lower surface of the annular seat contacts an upper surface of a valve element. The valve element moves slideably between an upper position and a lower position. Various combinations of differential areas and pressures result from the movement of the valve and the hammer to effect reciprocation of the hammer. Special valve stops are xed to a valve guide means to prevent the valve from striking the valve seat located 'or the hammer. This improves valve life.

'Ihis invention is a continuation-in-part of our copending application Ser. No. 491,116, led Sept. 29, 1965, now abandoned.

This invention relates to fluid actuated tools for applying repeated percussive blows to a drill bit in the drilling of oil and gas wells and the like. In particular, the invention is related to percussion motors for incorporation in drill strings, causing drill bits to vibrate or oscillate axially at the same time that they are being rotated for the drilling of such wells. The invention relates especially to improvements in valve means in percussion motors and especially to those percussion motors such as described in our co-pending application Ser. No. 596,374, iiled Oct. 24, 1966, now Patent No. 3,327,790.

A number of designs of percussion motors for drilling bore holes in the earth have been suggested in the past. Those which have had a measure of success in practice have been designed for use with a stream of high-pressure gas, such as compressed air or natural gas. The percussion motor is mounted at the lower end of the drill string and in turn is connected to a suitable drilling bit. The stream of high-pressure gas, circulating through the drill string, percussion motor, and bit, causes the bit to oscillate percussively against the formation and thus produce a major part of the drilling effect. The drill string is customarily rotated, both to produce a further drilling effect and to minimize deviations in the direction of the hole. The compressed gas from the percussion motor normally ows out ports in the bit and up the annulus between the walls of the hole and the drill string carrying formation cuttings and well fluids to the surface.

Although the use of compressed gas has proved quite advantageous in drilling of many wells, there are many situations encountered where compressed gas cannot be used as the drilling uid. Many times it is necessary to use liquid (customarily a water or an oil base drilling Patented Sept. 2, 1969 ICC iiuid) to control flows of formation iiuids into the well and to carry formation cuttings to the surface. It is well known that the hydraulic head imposed by the column of liquid in the borehole oifers control against flow of formation fluids into the Well bore. The previously used percussion motors which were designed primarily for compressed air or gas do not at all work well when the drilling fluid is a liquid. Our co-pending application Ser. No. 596,374 describes percussion motors which are especially designed for operations when the circulating drilling iiuid is a liquid. As mentioned in that application, even though drilling liquids returning ot the surface usually pass through vibrating screens and are circulated through settling zones in the mud pit, it is substantially impossible to produce a stream of material to be recirculated through the drill string which contains no quantity of abrasive solids. Accordingly, it is a very definite problem in the design of liquid actuated percussive drilling motors to maintain valve operations without excessive abrasion and resultant wear. It is therefore an object of this invention to provide an improvement in the valve system of a percussion motor, and especially for a liquid actuated percussion motor, although the improved valving system can be used with motors actuated by gas, if desired.

Other objects and a better understanding of the invention can be had from the following taken in conjunction with the drawings in which:

FIGURES 1A and 1B are lower and upper portions, respectively, of a cross section of a percussion motor utilizing the valving arrangement of this invention; and

FIGURES 2-6, inclusive, are digarammatic representations illustrating various phases during the operation of our percussion motor;

FIGURE 7 illustrates a lower portion, partly in section, of a modification of the percussion motor of FIG- URES 1A and 1B;

FIGURE 8 is a view, partly in section, of the upper portion of a percussion motor having a stepped differential area hammer which illustrates a modification of the stepped feature of the hammer of FIGURES 1A and 1B;

FIGURE 9 illustrates a special seal for use in the tool.

A percussion motor normally contains two basic moving parts which are a stepped piston type hammer and a central cylindrical valve assembly. Although this invention is primarily concerned with improved valving arrangement, such improvement involves both basic moving parts as the two cooperate to produce the desired valving. An explanation will be given of the entire motor and particularly how the valve assembly cooperates with the other parts to produce an improved over-all operation to obtain increased life for the tool. ln addition to the piston type hammer and valve assembly, a percussion motor has a casing or housing to confine the actuating fluid and an anvil slidcably mounted within the housing below the hammer; however, the anvil is arranged for only limited axial motion. The housing can transmit the customary down-ward force from the drill collars through the anvil to the bit. The anvil is arranged so that its upper face receives impacts from a lower face of the hammer upon its reciprocation. The lower end of the anvil is connected to the drilling bit. The anvil additionally is provided with splines and projections mating with similar splines and projections in the inside lower part of the housing so that torque applied to the drill string from the housing will rotate the drilling bit while percussive drilling is proceeding.

In operation, the percussion motor is mounted at the bottom of a string of drill pipe. The drill string is rotated from the surface and a high-pressure tiuid is directed downward through it. The iiuid does work in passing through the percussion motor and is exhausted from an exhaust passageway in the drill bit. The drilling fluid experiences a considerable drop in pressure as it passes through the drilling tool and drill bit; the pressure of the fluid in the annulus between the tool and bore hole normally being from 100 to 600 or 800 pounds, or more, less than the pressure of the fluid in the drilling string. This difference in pressure is used to advantage in reciprocating the hammer.

The central valve assembly oscillates between an upper and a lower position which causes a force to be applied alternately to the top and bottom of the slideable hammer, causing it to oscillate axially or vertically. After each upward stroke of the hammer, it is impelled downward to impact on the anvil, thus in turn causing the anvil lto apply a series of percussive blows to the drill bit in contact with the earth formation. As will be seen, the valve means is arranged to decrease wear, especially eroding of the valve members.

In the drawing, tubular housing is attached by sub 50 to the lower end of a conventional drill string (not shown). Tubular housing 10 includes an upper portion 12 of smaller inside diameter than that of the lower portion 14. There is a radial port 18 through the wall of the housing 10 below but near the junction 16 of the upper and lower portions.

A hollow stepped cylindrical hammer 20 is mounted for axial movement within housing 10. The upper outer diameter of hammer 20 is machined to closely lit in the upper portion 12 of housing 10. Similarly, the lower outer diameter of hammer 20 closely lits the adjacent lower portion 14 of housing 10. Seals 22 and 24 are preferably provided between the hammer and the housing in the upper and lower portions thereof. The tool includes a hollow bore 26 at its upper end which is in direct and free communication with the drill string when in operation. The tool is arranged so that there is essentially no leakage of fluid from hollow bore 26 to port 18.

An especially eicient seal is illustrated in FIGURE 9. These seals are adapted to be in groove 24A of FIG- URE 7, for example. These seals are ring-shaped and in cross section, when unconiined, take the shape shown in FIGURE 9. Left vertical line 150 represents the surface of the hammer and right vertical line 152 represents the position of the surface of the lower side of groove 24A of housing 10. When inserted in a tool they are confined between the lines 150 land 152. The seal has a lip 154 which makes a pocket 156. This pocket is subject to the high pressure that may exist in the clearance between the hammer 20 and the housing 10. Typical dimensions of the cross section of the seal of FIGURE 4 in its unconfned shape where line 152 of the seal has a radius of about 6.5 inches include an angle 158 between the plane of the lip 154 and a right angle to the base 160 of about 4. Angle 162 of face 164 is likewise about 4. The overall vertical thickness of the cross section is typically about .6 inch with section 166 being about .125 inch and length 168 being about 4.75 inches. Length 170 is about .288 inch and length 172 is about .312 inch. When the seal is inserted in the tool, it is confined between lines 150 and 152. High pressure fluid in chamber 156 forces lip 154 toward the line 152 and face 164 firmly against the hammer represented by line 150. The wearing surface is surface 164. As this surface wears, the pressure in cavity 156 forces the face outwardly to compensate for such wear.

Slideably mounted for limited axial movement in the lower end of housing 10 is anvil 28. At its lower end, anvil 28 is provided with means for transmitting torque from housing 10 to a drill bit (not shown) which is attachable to the lower end thereof in a conventional manner, such as by threads 30. Various variations of torque transmission arrangements can be used. One form is shown in FIGURE 1A in which the lowermost part of the housing has a plurality of vertical ridges 32 between each two of which are splines or grooves. These ridges 32 engage equivalent splines or grooves cut into lthe outer periphery of the lower portion of anvil 28. The lower portion 28A of anvil 28 is enlarged to approximately the same diameter as that of housing 10. Upper surface 102 of anvil portion 28A is designed to receive lower end of housing 10 so that a portion of the weight of the drill string above may be applied to the bit, thus improving its effectiveness in drilling. The splines in both the anvil 28 and the housing 10 are longer than the corresponding or mating ridges so that until the drill bit touches bottom, there is a vertical distance that anvil 28 can move between the position shown in FIG- URE 1A and a lower position in which adjacent splines and ridges are in top contact. Means not shown are provided to limit this vertical downward movement typically from about l to about 3 inches. As will -be seen, this extension renders the hammer inactive.

Anvil 28 is provided with a central bore 34. The top surface 36 of `anvil 28 mates with the bottom surface 38 of hammer 20. Surface 36 is provided with a plurality of grooves 40. Also provided in anvil 28 are a plurality of conduits 42 which extend from surface 36 to within bore 34. Grooves 40 are intersected by or otherwise in fluid communication with conduits 42. Grooves 40 can extend into cylindrical valve well 77. These grooves and conduits, singly or in combination, permit the liquid between the hammer and anvil to be quickly evacuated so as not to cushion impact between the two.

Conduit 42 also serves to permit the tool to start under certain conditions when otherwise it would not. Consider now the tool in the position of FIGURE 2. If the seal 24 is effectively provided between anvil 28 and housing 10 under certain conditions uid can be trapped in annular space 89 if it were not for conduit 42. When this happens, hammer 20 cannot go down unless the fluid in chamber 89 is displaced. This is so because valve 58 is seated in annular seat 78 of anvil 28 and the internal valve ring 82 forms a valve with element 86 of the valve guide 46. The escape of fluid from chamber 89 when the tool is in this position is downwardly through conduit 42.

A center valve or guide tube 46 is supported in housing 10 which is connected by threads to sub 50. A ball joint 48 is secured to the upper end of guide tube 46 and mates with ball joint socket 47 which is mounted in recess 51 of sub 50. Spacer 49 and spacer spring 49A hold the ball joint and socket in position. Near the lower end of the guide tube, web type guide means 53 supported within the hammer is provided to accurately center the tube within the hollow portion of the hammer. It has been found that this manner of mounting tube 46 permits more precise centering than when the tube is rigidly attached to sub 50 such as by threads.

As shown in the drawing, sub 50 also provides the means for connecting to the drilling string. Center valve tube 46 is provided for use in controlling movement of the Valve assembly. Tube 46 is preferably a thin-walled pipe of uniform diameter, concentrically mounted in housing 10. The upper end of valve tube 46 is in direct fluid cornmunieation with uid channel 26. The upper end of valve guide tube 46 is provided with a plurality of ports `52 which are of sufficient size and number so that there is very little pressure drop between the pressure of the uid in the uid channel 26 and fluid channel 55 which is the annular space between the exterior of valve tube 46 and the interior of hammer 20. A main valve assembly is provided for the lower end of valve tube 46 and includes a valve stern 54, a valve piston 56, and valve head 58 having an upper surface 58A and a lower surface 58B. Valve piston 56 is sealingly tted within the lower end of valve tube guide 46. Annular valve head 58 is connected to the lower end of valve stem 54. Valve stern 54 slidingly extends in a sealing relationship through end member 60 of valve tube 46. I ust above end member 60 are a plurality of ports 62 in the wall of valve tube 46. The relationship of the location of these ports to the rest of the tool when anvil 28 is in its lower position will be discussed hereinafter. Valve stem 54 is of a sucient length that when the moving parts of the tool are in the position shown in FIG- URE 1 of the drawing, there is a cavity 64 within valve tube 46 below valve piston 56. When piston S6 is above ports 62, cavity 64 has the same pressure P3 as the pressure in annulus 55 between valve tube 46 and hammer 20. This pressure acts against an area AVP which is the horizontal component of the area of the lower side of valve piston 56 which is in communication with cavity 64. Mounted within valve tube 46 above valve piston 56 is a fluid restriction means which is shown in the drawing as being a nozzle or choke 66. This nozzle functions so that the pressure P1 Within the interior 45 of valve guide tube `46, between piston 56 and nozzle 66, is always substantially less than pressure P3 in the annulus between the valve tube 46 and the hammer with an exception which will be shown later when ports 62 are in communication with interior 4S. In other words, this arrangement provides a reduced pressure to act downwardly against the effective horizontal component AVP of the valve piston 56. Nozzle 66 should be a sufficient distance above piston 56 so that no appreciable jetting action is imparted to the valve piston.

A positive stop 68 is provided in valve guide tube 46 to limit the upward movement of valve assembly (54, 56, S8) to a predetermined position which will be explained hereinafter. As will be shown, `the stop and its position are very important in greatly increasing the life of the valving means. Stop -68 is preferably made of a hard metal to withstand Wear. The stop is illustrated as a stepped annular member and is held in position by anchor means such as an annular member 70, which complements annular stop 68, and which is rigidly secured to valve ,guide tube 46 such as by welding or made an integral part thereof. A shock absorbing material 72 is provided between positive stop 68 and anchor means 70. Such a shock absorbing material can be an elastic material such as rubber or a spring. The lower side of stop 68 may also include grooves 74 which act as a fluid cushion which aids in reducing impact fatigue of the piston. These shock absorber features are quite important and greatly reduce the wear and impact fatigue of valve piston 56 and stop 68.

FIGURE 7 illustrates a particularly desirable form of means for stopping the upward movement of the valve assembly (54, 56, SS). This can, in effect, be considered a dashpot-type stop. The upper end of valve head 56 is modified to include annular-like cavity 56C. The lower end of valve guide tube 46 has been modified to have a downwardly facing cavity 47. This cavity 47 is annular in shape and the size of cavity 47 is such as to slideably receive the upper end of valve head 56 which forms cavity 56C. The entrapment of fluid in cavities 47 and 56C when the upper end of valve head 56 reaches the lower surface 46A of the valve guide causes a very effective dashpottype stopping of the upward movement of the valve assembly.

Both the upper 58A and lower 58B surfaces of valve head 58 function as valves. Attention will first be directed toward a consideration of the seat assembly for the lower side of valve head 58 of the reciprocating main valve assembly. An anvil valve recess 76 is provided inthe upper end of anvil 28. This can be a cylindrical recess which in effect can be an enlargement of bore 34. Seat 78 is mounted in valve recess 76. The upper part of recess 76 above seat 78 is called a valve pocket 77 formed by ring member 77A which has a diameter only slightly larger than the diameter of valve head 58. Typically the clearance can be from about .()10 to about .080 inch. The interior of the pocket 77 and the exterior cylindrical surface of valve head 58 form in effect a sleeve valve which reduces the flow of fluid before valve 58 seats on annular seat 78. Annular seat 78 provides a seat for the lower surface 58B of valve head 58. The largest diameter of valve head 58 is greater than the diameter of piston 56. This provides for proper diterential areas. The top surface of annular valve, or anvil seat 78, is below the top surface 36 of the anvil a distance sucient so that essentially all of valve head 58 is received within the valve pocket 77. Mounted below the lower side of annular valve seat 78, which is in the lower part of valve recess 76, is a shock absorbing means 80. This absorbing material can be similar to material 72 which is provided with positive valve stop 68. It aids in reducing impact stresses in valve head 58 and annular valve seat 78, both of which are preferably made of a hard metal, such as tungsten carbide. Valve head 58 when closed against anvil seat 78 prevents flow of fluid from annulus 55 to bore 34 within anvil 28. The pressure within bore 34 is designated for convenience P2 and when valve 58 is closed against seat 78, P2 approximates the pressure exterior of the tool (and also P1 within valve tube guide interior 4S), since when the tool is closed, flow of uid through the bit stops (except a small amount flowing through choke 66) and pressure in bore 34 approximates the pressure exterior of the tool.

Valve head 58 includes a carefully machined upper surface 58A, as well as a carefully machined lower surface 58B. Near the bottom of stepped hammer 20, the bore of the hammer is decreased and an annular sleeve valve member 88 is provided forming a hammer valve pocket which is equal in depth to or slightly deeper than the distance separating seats 58A and 58B. This depth requirement is important and is clearly shown in FIGURE 1A. An annular valve seat is provided above annular member 88 for the upper surface 58A of valve head 58. Shock absorber rings 92 are provided for annular valve seat 90. A retainer 93, which can be an extension of annular Valve 82 described below, is provided for the shock absorber and anchors the shock absorbers and valve 90 against upward movement with respect to hammer 20. It will be noted that when the valve head 58 is in its closed position in the anvil, i.e., lower surface 58B on seat 78, and its upper surface 58A is not in contact with valve seat 90 nor in hammer valve pocket 85 when hammer 20 is in its lower position. This permits high pressure fluid to act on the lbottom surface of hammer 20, thus forcing it upward.

Attention will now be directed toward a secondary 0r annular valve which can lbe referred to as a ring tvalve. This includes an annular ring valve 82 mounted on the interior of the lower end of hammer 20` above shock absorber retaining ring 93. Ring valve 82 preferably is provided with hard facing 84. The lower portion 86 of lower member 60 of valve guide 46 is preferably a hard metal, such as sprayed-on tungsten carbide, and is carefully machined as is the interior of the hard facing 84 of the ring valve 82 so that as hammer 20` moves upwardly, ring 'valve 82 cooperates with the lower portion 86 to stop substantially all of the flow of fluid downwardly from annulus SS. There will still be flow from annulus 55 to cavity 64 while the valve assembly 54, S6, 58 is moving upward.

Having described the general configuration of the drilling tool, attention will now be directed toward its operation and particularly toward the inner relationship of different parts `of the valve which have been found to be most important. An operating cycle can begin with the parts in the relative positions illustrated in FIGURES lA and 1B. There it can be seen that the primary valve, that is, valve head S8, is seated on the anvil valve seat 78 and hammer 20 is resting upon anvil 28. A consideration of the predominant forces on the valve and hammer when fluid pressure is applied through the drill string will now be made for each of the positions indicated in FIGURES 2-5 and FIGURES 1A and 1B. FIGURES 2-6 are drawn to illustrate primarily relative positions of the various parts for different phases of an operational cycle rather than relative size. The hammer will start up from the position shown in FIGURE lA because the net force on the hammer is up. This is shown by a consideration of the dominating hydraulic forces. The downward force on hammer 20 is where A is the upper horizontal component of the area of the stepped hammer in contact with the fluid having pressure P2, which is the pressure of the fluid in the annulus exterior of the tool; A, is the horizontal component of the upper area of the stepped hammer in communication with the main stream of drilling fluid in annulus 55 at a pressure P3. The upward force on hammer 20 is where A6 is the horizontal component of the area of the lower surface of the hammer. As A6 equals A5 plus A7, it is readily apparent that there is an upward force on hammer 20 due to the differential pressure.

The force on the valve assembly while the hammer is rising (and before ring valve 82 seats with or closes over seat 86 on exterior of valve guide member 46) will now be given. The force down is (3) Pa(vH-Avs) -l-P1(AvP-Avs) and the force up is (4) P3(AvP-Avs) +P'1(AvH-AVS) where AVH is cross-sectional area of valve head 58; AVS is cross-sectional area of valve stem; and AVP is cross-sectional area of valve piston S6. P3 is the larger pressure within cavity 64 and annulus 5S. P1 is the reduced pressure of the fluid Within bore 34, and as there is little ow at this moment between bore 34 and the exterior of the tool, except for the amount passing through choke 66, for this explanation it can Ibe considered that P1 is also the approximate pressure P1 of the uid in the annulus eX- terior of the tool.

The net force at this time on the valve assembly is down and is as AVH is greater than AVP by construction.

Valve head S8 stays closed, i.e., seated in the anvil, until hammer 20 rises to a position shown in FIGURE 2 and the secondary valve closes, i.e., ring valve 82 mates with the lower portion 86 of valve guide 46. When this occurs, the cavity 87 below member 86 and exterior of stem 54 is shut off from the main stream of drilling fluid. As soon as annular member 84 is adjacent the lower end 86 of tube 46 it reduces the flow of fluid into cavity 87. This reduction in uid flow is accompanied by a substantial decrease in pressure beneath hammer 20 since also the volume of the chamber 89 between the hammer 20 and the anvil 28 is expanding. When pressure in chamber 89 decreases sufficiently, the valve assembly will be forced up. The net force on the valve assembly is where a positive designation represents upward force and negative sign represents a downward force.

P'3 is approaching P2 because the volume of the cavity 87 and chamber 89 between the ring valve, i.e., upper annular valve 84, and the anvil face is expanding faster than uid can leak past the ring valve. Therefore the net upward force on the valve is As this value is positive and P3 is much greater than P1 and AVH is only slightly larger than AVP, the lvalve assembly is literally thrown upwardly. FIGURE 3 is similar to FIGURE 2 but shows the valve 58 at about one-half way up between the anvil and hammer seat. The valve continues upwardly until it encounters stop 68 as illustrated in FIGURE 4. Stop 68 is positioned so that the valve assembly is stopped before valve head 58A contacts annular ring 90. If the valve were stopped by annular ring 90, then as the hammer and valve assembly move upwardly, cavity 8'5 would be decreasing in volume and the fluid captured therein would be increasing rapidly in pressure. This would cause the fluid to forcibly How by the valve surface 58A and valve seat v90, causing severe erosion. In this invention, valve stop 68 is thus positioned so that when the secondary Valve, i.e., ring valve 82 closes, cavity 87 cannot shrink in an enclosed position after valve head 58 is stopped. Stop 68 is so placed that valve head 58 is stopped at a position just below val-ve seat 90 when the hammer is in its upper position. The valve stop 68 is also positioned so that the ring valve 82 is still closed (i.e., engaging valve member 86) when the annular ring contacts valve head 58A on the hammer downstroke. One way of accomplishing this is to place stop 68 so that the valve assembly is stopped after valve head S8, reaches a distance lz, or preferably slightly less than h, from the point 17 on face 86 where h is the distance from valve seat 90 to the upper end of hard facing 84 of ring valve 82. This assures that cavity 87 cannot shrink with fluid in it in a closed condition. Valve surface 58A should seat with seat 90 before surface 84 of ring member 82 travels downwardly suicient to clear point 17 on Valve guide tube 46.

A tool was constructed which has a 7" O D. casing, a 5.375" O.D. hammer, a 2.375 diameter valve piston, a 1.625 diameter 'valve stem, and a 2.750 O D. valve portion 86 on lvalve guide 46. In that tool, the top of ring 82 in its uppermost position is about .040" to .250 above the point or boundary 17. In that tool the stop 68 is preferably set so that surface 58A is stopped at distance equal to h minus about .100 inch below point 17.

A brief consideration of the predominant force on the valve assembly (disregarding the force due to the weight of the assembly itself) will now be given when the various parts are in the position shown in FIGURE 4 in which piston 56 is against stop 68, ring valve 82 still closed and yalve S8 not seated any-where. The net force on the valve 1s where the plus force is acting up and the negative down. Since P3' approaches P1 then the net force is (P3-P1)AVP which is positive as P3 is much greater than P1.

When the flow of uid is shut off or reduced beneath the surface A6 of the hammer and valve 58 is stopped, the net downward force on the hammer rapidly exceeds the upward force and the hammer is forced downwardly. (On most of the down stroke the valve unit and hammer travel together.) When hammer 20 starts down, cavity 87 is increasing and essentially no fluid flows between seat 90 on the hammer and the upper valve surface 58A of the valve as it closes. In other words, after some downward movement, the hammer through valve seat 90 forces the valve down with it. The relative position of the parts are shown in FIGURE 5. The upward force on the lvalvc is greater than the downward force because of the seal between the valve head 58A and the valve seat 90. 'Ihe net force on the valve assembly due to iluid pressure 1s where a positive designation is au upward force and a negative designation indicates that that force is downward, and AHS is the area of valve head 58 in contact with fluid pressure P3. By design, AVH is greater than AVP which is greater than AHS. Therefore the net force on the valve assembly is upward. The inside diameter of tube 46 is made greater than the minimum diameter of seat 90. When the hammer impacts the anvil, the hammer will stop; however, the inertia of the valve will yunseat it from the annular seat 90 and start the valve toward its seat 78 in the anvil as shown in FIGURE lA. Now the valve no longer has a net upward force. The valve pocket 85, in closely fitting valve 58, serves a very useful purpose as it enables a pressure differential to be maintained across valve element 58 so that it will continue to go down to seat 78. Valve pocket 77 also closely fits head 58 which a valve stop fixed to said valve guide and positioned such that said valve element when in its upper position is spaced from said annular valve seat on said hammer when said hammer is in its upper position and further that in its upper position said valve element is not over a distance h below the lower line of contact of said peripheral surface of said valve guide.

3. A percussion drilling device comprising:

(a) a tubular housing having a fluid intake containing an upper portion of smaller inside diameter than that of the lower portion thereof, there being a port through the wall of said housing below but near the junction of said upper and said lower portion;

(b) a tubular valve guide member substantially concentrically mounted within and stationary with respect to said housing, the upper part of said tube being in uid communication with the fluid intake to said device;

(c) a valve assembly including a cylindrical valve element and a piston tting the inside of said tubular valve guide member, a stern of lesser diameter connecting said valve element and said piston, there being a longitudinal passageway through said valve assembly;

(d) a hollow, stepped cylindrical hammer slideably mounted between a lower and an upper position within said housing and around at least a portion of said valve guide member with an upper outer diameter tting the upper portion of said housing and a lower outer diameter fitting the lower portion of said housing, the upper surface of the upper part of said hammer being in uid communication with the fluid intake of said housing, the inner diameter of said hammer generally exceeding the outer diameter of said valve guide member, said hammer carrying above the bottom thereof a first annular member having an internal diameter approximately the same as the outside diameter of said tubular valve guide member so as to essentially stop the flow of uid in the annular space therebetween when said hammer is in a first position and to permit free ow when said hammer is in a second, lower position, said hammer additionally carrying a fixed distance below said first annular member a second annular member above but near the bottom of said hammer, the least inside diameter of which is less than the maximum diameter of said piston, and which is adapted to form a seat for the upper side of said valve element;

(e) a stop in said tubular valve guide member limiting the upward movement of said valve assembly such that the upper side of said valve element is spaced from said seat of said second annular member when said hammer is in its first position but such that the upper surface of said valve element when in its upper position is in contact with said second annular member of said hammer when said first annular member clears said tubular valve guide means;

(f) a hollow cylindrical anvil slideably fixed within and fitting the lower portion of said casing with the top thereof below the bottom of said hammer, said anvil being so shaped relative to said casing as to transmit axial torque, the bottom of said anvil being shaped for coupling to a drill bit, the upper end of the hollow part of said anvil being enlarged to form a recess to receive said valve element and so shaped adjacent the top to form a seat for the lower side of said valve element, the greatest diameter of said seat exceeding the diameter of said piston.

4. An apparatus as defined in claim 3 in which the top of said anvil is provided with grooves in fluid communication with the hollow portion of said anvil.

5. An apparatus as defined in claim 4 in which conduits, having greater ow resistance than the hollow porl2 tion of said anvil, are provided within the body of said anvil for connecting said grooves in the top of said anvil with the hollow central portion thereof.

6. .An apparatus as defined in claim 3 in which said stop includes shock absorbing material provided between the impact surface of said stop and its attachment to said valve guide.

7. An apparatus as defined in claim 3 in which said seat for said Valve is recessed below the surface of said anvil a sufiicient distance so that on each down stroke of said hammer, said anvil is struck by said hammer before said valve element seats in said anvil and in which shock absorber means is provided between said anvil and said valve seat in said anvil.

8. A device as defined in claim 3 in which shock absorbing means is provided between the upper side of said second annular member and its attachment to said hammer.

9. A percussion drilling tool for drilling a bore hole and attachable to the lower end of a string of drill pipe, which comprises:

(a) a tubular housing adapted to be connected to said drill string and including a drilling fluid passage in the upper end thereof, said housing containing yan upper portion of smaller inside diameter than that of a lower portion',

(b) a hollow anvil mounted in the lower end of said tubular housing, the upper end of said anvil having a cylindrical recess and a seat therein, said anvil including conduits extending from its upper surface to its hollow interior;

(c) an annular stepped hammer having an upper extension `of lesser diameter than the lower portion thereof and positioned in said tubular housing above said anvil and movable between an upper position and a lower position whereby said hammer strikes said anvil, the exterior of the stepped extension of said hammer with said housing forming an annular cavity between said hammer and said tubular housing, said cavity being in fiuid communication with the exterior of said tubular housing, said hammer having an upper surface of its lower portion within said cavity, an upper surface of its extension in fluid communication with the drilling fluid passage of said housing and a lower surface, for striking said anvil;

(d) a cylindrical valve guide fixed to said housing and extending into the hollow portion of said hammer, there being an internal annular shoulder near the lower end of said valve guide forming a passage of reduced diameter, said guide including ports in the wall of said guide immediately above said shoulder, the exterior of said valve guide being of a smaller diameter than the inside of said hammer thus forming an annular space;

(e) means establishing fluid communication between said drilling iiuid passage and the annular space between said valve guide and said hammer;

(f) a valve assembly having a longitudinal passage therethrough and an upper enlarged member positioned and sealingly fitting within said Valve guide above the internal annular shoulder thereof and a lower enlarged end member exterior of said valve' guide, the lower enlarged end member seating within said cylindrical recess of said anvil;

(g) a first annular valve seat element on and recessed within the lower end of said hammer for engagement with the upper side of said lower enlarged end member of said valve to form a valve means;

(h) an annular ring valve on the lower interior of said hammer above said first valve seat element and complementing the exterior of the lower end of said valve guide to form a valve means;

(i) a chocke in the upper end of said valve guide in fluid communication with said drilling fluid passage; and

together with valve pocket 85 prevents valve head 58 from prematurely returning to seat 90 where it might seat and lock the assembly. Of course, the tool could be Iunlocked merely by raising it off bottom while maintaining the drilling fiuid under pressure. Further, any tendency of the valve to bounce from seat 78 is reduced by the close fit of valve head 58 in valve pocket 77.

The hammer 20 impacts on the top face of anvil 28. It is important that there be no restriction in motion of the hammer just as it is about to strike the anvil. Accordingly, it is desirable, though not essential, to provide the aforementioned radial grooves 40 in the upper end of anvil 28 and conduits 42 so that liquid remaining between these faces of the hammer and anvil can be ejected rapidly into the exhaust passageway 34. The flow resistance through conduits 42 is much greater than through bore 34. This permits maximum impulse during the transfer of momentum of hammer 20 to anvil 28. Grooves 40 can be in the lower surface of the hammer if desired.

It is seen that the valve elements and the means for limiting its travel are provided to prevent excess wear on the valve mechanism. The valve element, being much lighter than the hammer, is forced upward at a higher velocity than is the hammer. However, in this design, it is seen that the upward movement is stopped by especially designed stops which very importantly are provided with shock absorbing material and most importantly, the part of the assembly which is the actual valve is not involved in the stopping of the upward motion. It is further seen that the downward motion of the valve is occasioned by hydraulic pressure acting on the hammer and the hammer carries the valve assembly downward at hammer velocity, not at the velocity with which valve assembly was carried upward. In this event, it is also seen that the valve seat 90 on the hammer is provided with shock absorbing means 92 to aid in protecting the upper surface of valve head 58. When valve S8 seats with the anvil valve seat 78, this seat too is provided with shock absorbing means 80. It is thus seen that the valving assembly is provided with features which minimize wear or damage to the valving system, yet permits it to operate at the required reciprocation rate.

If it is desired to circulate through the tool without reciprocating the hammer, all that is necessary is to raise up on the tool. The parts then take the relative positions indicated in FIGURE 6. There the fluid circulates primarily from annulus 55 between the hammer 20 and the valve guide 46 through ports 62 to interior 45 above valve piston 56; then down the large hollow portion 57 of the valve assembly to bore 34 of the anvil. This also forces hammer 20 upward so that ring valve 82 is closed. If it is desired to so circulate, a port in the wall of guide tube 46 should be near its lower end as indicated by port 62A so that fluid will not be trapped below piston 56 which would prevent downward movement. Hammering of the tool from the position illustrated in FIGURE 6 can be commenced while circulating fluid merely by lowering the tool until the bit contacts the bottom of the bore hole, forcing anvil 28 and the valve assembly 54, 56, 58 seated on anvil seat 78, upward until piston 56 moves up to close off valve tube ports 62.

Certain modifications of the tool improve its operation. For example, the addition of the shear pin (shown sheared as portions 174A and 174B) between the lower section of the housing and the anvil is quite useful. This prevents movement of the anvil while going into the hole. If the anvil is held fixed with respect to the housing in its lowermost position, then fiuid can be circulated and reaming operations and the like done while lowering the tool without the hammer attempting to reciprocate. Without a shear pin, the hammer attempts to reciprocate, and while being lowered, when the bit and anvil hit irregular portions of the bore hole wall, the hammer, relatively speaking, falls to its lower position. When this occurs, cuttings sometimes accumulate in ports 18 and the space above the upper end of the stepped hammer which is in fluid communication with the exterior of the tool. If the accumulation of cuttings is sufiicient, it can cause the tool to be stuck. However, by adding a shear pin, the tool cannot reciprocate, and the hammer is in its upper position until the tool reaches bottom. The difficulty of the accumulation of cuttings is thus prevented. After the tool reaches bottom, the bit can rest on the bottom of the hole and weight added to the drill string until the shear pin is sheared. The pin is shown in FIG- URE 7 as having been sheared. It includes an outer portion 174A in the housing and the inner portion 174B in the anvil. After the pin has been sheared, the tool operates in its usual manner.

The embodiment of FIGURE 8 features an inverted stepped hammer. Hammer 20A has an upper section 176 which has a larger internal diameter than the lower section 178. This provides an upwardly facing shoulder between the two which is subject to the high pressure uid in the passage between the hammer and the valve guide tube 46. Upper section 176 has its interior sealed with seals 182 with downwardly extending tubular member 184 which is fixed to the housing. Upper hammer section 176 has upper shoulder 186 which is in fluid communication with the exterior of the tool through ports 188.

While there are disclosed above a limited number of illustrations of this invention, various modifications can be made thereto without departing from the spirit and scope of the invention. Therefore the scope of the invention is defined by the appended claims.

We claim:

1. In a percussion drilling tool including a housing, an axially hollow hammer slideably disposed within and closely fitting said housing and movable between an upper position and a lower position, an axially hollow anvil slideably disposed within and closely fitting said housing and positioned adjacent one end of said hammer, said hammer being reciprocated between an upper position away from and a lower position contacting said anvil by valve action of valve means on a iiuid stream flowing in the axial hollow portion, said valve means including an inner annular valve seat on said hammer which is positioned such that the lower surface of said annular seat contacts an upper surface of a valve element, said ele ment moving slideably between an upper position and a lower position and guided by valve guide means supported from said housing within said hammer, the improvement which comprises:

a valve stop fixed to said valve guide means and positioned to stop upward movement of said valve element such that said valve element when in its uppermost position is spaced from the said annular valve seat on said hammer when said hammer is in its upper position.

2. In a percussion drilling tool including a housing, an axially hollow hammer slideably disposed within and closely fitting said housing and movable between an upper position and a lower position, an axially hollow anvil slideably disposed within and closely fitting said housing and positioned adjacent one end of said hammer, said hammer being reciprocated between an upper position and a lower position by valve action of valve means on a fiuid stream flowing in the axial hollow portions, said valve means including an inner annular valve seat on said hammer which is positioned such that the lower surface of said annular seat can contact an upper surface of a valve element disposed slideably between an upper position and a lower position and guided by valve guide means supported from said housing within said hammer, said valve means additionally including an inner ring member supported on said hammer whose top is a fixed distance It above said annular valve seat, such ring member together with a peripheral external surface (having a lower line of contact) on said valve guide forming a ring valve, the improvement which comprises:

(j) stop means in said valve guide and supported thereby for limiting the upper movement of said enlarged end member of said valve to a position spaced below said annular valve seat of said hammer when said hammer is in its upper position.

10. A tool as defined in claim 9 in which the lower enlarged end member of said valve assembly is made `of a hard metal.

11. A tool as defined in claim 9 in which said stop means includes a face of a hard metal surface for contacting said valve on its upward motion and shock absorbing means between said face of hard metal and said valve uide.

g 12. A tool as defined in claim 9 in which said seat in said anvil for said valve is recessed below the surface of said anvil a sufiicient distance so that on each downstroke of said hammer, said anvil is struck by said hammer before said valve seats in said anvil and in which shock absorbing means is provided between said anvil and said valve seat in said anvil.

13. A liquid actuated percussion drilling device comprising:

(a) a tubular housing containing an upper portion of smaller inside diameter than that of the lower portion thereof, there being a port through the wall of said housing below but near the junction of said upper and said lower portions;

(b) a center valve guide tube substantially concentrically mounted within said housing with at least a part thereof extending down into the lower portion of said casing, said tube having a side port therein;

(c) means for maintaining the central internal portion of said tube above said side port at a pressure substantially below that of the fluid intake to the device;

(d) a valve assembly including a cylindrical valve element and a piston fitting the inside of said tube, said valve element and said piston being connected a xed distance appart by a hollow connecting stem;

(e) an annular member in said center tube at the lower end thereof and below said side port, said member having a central passage closely fitting the exterior of said connecting stem, said member being so located that when said piston contacts said member at least the upper part of said side port is above said piston;

(f) a hollow, stepped cylindrical hammer slideably mounted within said housing and around said valve guide tube with the upper outer diameter fitting the upper portion of said housing and lower outer diameter fitting the lower portion of said housing, the inner diameter of said hammer generally exceeding the outer diameter of said valve guide tube, said hammer carrying above the bottom thereof an annular member shaped to slideably fit said tube to form a ring valve adapted to reduce fluid communication between the bottom of said hammer and the annulus between said hammer and said tube when said annular member fits said tube, said hammer additionally carrying below said annular member a second annular member above but near the bottom of said hammer, and spaced a fixed distance h below said first annular member, the least inside diameter of said second annular member being less than the diameter of said piston, and which is adapted to form a seat for the upper side of said valve element to thus form an annular valve;

(g) a hollow cylindrical anvil slideably constrained within and fitting the lower portion of said housing in splined relation thereto, with the top of said anvil below the bottom of said hammer, the bottom of said anvil being adapted for coupling to a drill bit, said anvil being shaped adjacent the top to form a seat for the lower side of said valve element, the greatest diameter of said seat exceeding the diameter of said piston; and

(h) a stop in said tube above said side port limiting the upward movement of said valve assembly such that the said cylindrical valve element when in its upper position is at about said distance h below the point at which said annular member fits said tube.

14. A device as defined in claim 13 in which said stop includes a face of a hard metal surface for contacting said piston on its upward motion and shock absorbing means between said face of hard -metal and said tube.

15. A device as defined in claim 13 in which the wall of said anvil contains conduits establishing fluid communication between its hollow interior below said anvil seat and its top, such conduits having substantially more resistance to the flow of fluid than does the hollow interior of said anvil.

16. A fluid actuated percussion drilling device comprising:

(a) a tubular housing having a fluid intake and containing an upper portion of smaller inside diameter than that of the lower portion thereof, there being a port through the wall `of said housing below but near the junction of said upper and said lower portions;

(b) a center valve guide tube having a side port near its lower end;

(c) means for mounting said valve guide tube substantially concentrically within said housing, such means including a ball joint fixed to the upper end of said valve guide tube, a ball joint socket concentrically mounted in the upper end of said housing and a center guide means attached to the lower end of said valve guide tube means; Y

(d) means for maintaining the central internal portion of said tube means at a pressure substantially below that of the fluid intake to the device;

(e) a valve assembly including a cylindrical valve element and a piston fitting inside of said tube, said valve element and said piston being held a fixed distance apart by a hollow -connecting stem;

(f) the lower end of said valve guide tube having an enlarged member with a central passage and closely fitting the exterior of said connecting stem, said enlarged member being so located that when said piston is in -contact with said enlarged member, at least the upper part of said port is above said piston;

(g) a hollow, stepped cylindrical hammer slideably mounted within said housing and around said guide tube with the upper outer diameter fitting the upper portion of said housing and a lower outer diameter fitting the lower portion of said housing, the inner dlameter of said hammer generally exceeding the outer diameter of said valve guide tube, said hammer carrying above the bottom thereof an annular member shaped to slideably fit said tube to form a sleeve valve adapted to reduce fluid communication between the bottom of said hammer and the annulus between said hammer and said tube when said annular member fits said tube, said hammer additionally carrying below said annular member a second annular member above but near the bottom of said hammer, and spaced a fixed distance h below said first annular member, the least inside diameter of said second annular member being less than the diameter of said piston, and which is adapted to form a seat for the upper side of said valve element to thus forrn an annular valve;

(h) a hollow cylindrical anvil slideably constrained w1thin and fitting the lower portion of said housing in splined relation thereto, with the top of said anvil below the bottom of said hammer, the bottom of said anvil being adapted for coupling to a drill bit, said anvil being shaped to form a recess adjacent the top to form a seat for the lower side of said valve element, the depth of said recess being greater than the thickness of said valve element whereby Said hammer strikes said anvil before said valve element is seated in said recess, the greatest diameter of said seat ex- -ceeding the diameter of said piston; and (i) a stop in said tube above said side port limiting the upward movement of said valve assembly such that the said cylindrical valve element when in its upper position is about said distance h below the point at which said annular member tits said tube. 17. In a percussion drilling tool including a housing, an axially hollow hammer slideably disposed within and closely tting said housing and movable between an upper position and a lower position, an axially hollow anvil slideably disposed within and closely tting said housing and positioned adjacent one end of said hammer, said hammer being reciprocated between an upper position L Y away from and a lower position contacting said anvil by valve action of valve means on a fluid stream Howing 1n tioned such that the lower surface of said -annular seat contacts an upper surface of a valve element, said element -moving slideably between an upper position and a lower position and guided by valve guide means supported from said housing within said hammer, the improvement which comprises:

valve stop means comprising the upper end of said valve means shaped to form an annular member, and an annular cup means opening downwardly and secured to said valve guide means, said annular cup means being of a size such that it can slideably receive said annular member, said annular member being in position such that when it enters said annular cup said valve element in its uppermost position is spaced from the said annular valve seat on said hammer when said hammer is in its upper position.

18. An apparatus as defined in claim 17 in which said anvil is provided with conduits in the body thereof for connecting the top of the anvil with the hollow central portion thereof.

19. An apparatus as defined in claim 17 in which the said hammer has an upper portion of a larger inside diameter than the inside diameter of the lower portion of said hammer; and including a cylindrical member whose outer diameter is slightly less than the inner diameter of said upper portion of said hammer, the upper end of said cylinder member being supported from said housing, said cylindrical member being positioned inside the upper end of said upper portion of said hammer;

sealing means between said upper portion of said hammer and said cylindrical member.

20. A percussion drilling tool as defined in claim 1 which comprises:

said hammer having an upper portion of a larger inside diameter than the inside diameter of the lower portion of said hammer;

a cylindrical member whose outer diameter is slightly less than the inner diameter of said upper portion of said hammer, the upper end of said cylinder member being supported from said housing;

sealing means between said upper portion of said hammer and said cylindrical member.

21. A percussion drilling tool including a housing, an

axially hollow hammer slideably disposed within and closely fitting said housing and movable between an upper position and a lower position, lan axially hollow anvil slideably disposed within and closely fitting said housing and positioned adjacent one end of said hammer, said hammer being reciprocated between an upper position away from and a lower position contacting said anvil by valve action of valve means on a fluid stream iowing in the axial hollow portion, said valve means including an inner annular valve seat on said hammer which is positioned such that the lower surface of said annular seat contacts an upper surface of a valve element, said element moving slideably between an upper position and a lower position and vguided by valve guide means supported from said housing within said hammer, the improvement which comprises:

valve travel limiting means at least partially supported by said valve guide means and positioned to stop upward movement of said valve element such that said valve element when in its uppermost position is spaced from said annular valve seat on said hammer when said hammer is in its upper position,

said hammer having an upper portion of a larger inside diameter than the inside diameter of the lower portion of said hammer;

a cylindrical member whose outer diameter is slightly less than the inner diameter of said upper portion of said hammer, the upper end of said cylinder member being supported from said housing;

sealing means between said upper portion of said hammer and said cylindrical member.

22. A percussion drilling tool as deiined in claim 21 in which said sealing means includes an annular sealing ring having a cross-section having a configuration of two parallel ends, a center line and two sides;

a rst side having a lip which extends less than one half the distance between the parallel ends, the outer side of said lip being tapered inwardly toward said center line at an angle of about 4;

the other side having two sections, the first section being much closer to the center line than the second section, said second section sloping from one end inwardly towards said center line at an angle of about 4, said second section not extending as far in one direction as said lip does in the other direction.

23. A drilling tool as defined in claim 21 including a shear pin holding said anvil in its lowermost position to said housing.

References Cited UNITED STATES PATENTS 2,774,334 12/1956 Cline 173-136 X 3,154,153 10/1964 Wilder 173-80 X 3,167,136 l/1965 Cook 173-80 X 3,198,264 8/1965 Oelke 173-73 3,311,177 3/1967 Collier 173-80 3,327,790 6/ 1967 Vincent 173-73 3,387,671 6/1968 Collier 173-73 NILE C. BYERS, I R., Primary Examiner Us. c1. Xn. 173-134, 137 

